This invention relates to liquid level sensing circuitry and in particular to such circuitry suitable for the electronic detection of engine crankcase oil level for determining whether the oil is at an acceptable or unacceptable level.
Monitoring of the crankcase oil level for essentially all automobiles and engine driven equipment presently in use is carried out by the visual inspection of the oil level as indicated on a dip stick that must be manually withdrawn from an engine. Heretofore, gasoline station attendants carried out this messy procedure for automobiles as a service to customers, but the extent to which that service is available has dwindled due to the establishment of self-service gasoline stations. The burden of carrying out this messy task is left to the automobile operator who is generally reluctant to carry out the task because of its very messy nature. Many times the task is deferred until it can be done without soiling clothing and/or hands or until someone else can do it. This, of course, leads to long periods between oil level checks which in turn results in otherwise avoidable damage to the engine due to operation of the engine with a low crankcase oil level. While many automobiles have an oil pressure indicator that presents an indication when there is an oil pressure problem, the appearance of such an indication due to a low oil level is usually untimely in that the engine has already been operating at an unacceptable level for a long period of time.